After the initial code changes were approved in June 2019, block number 9,069,000 was successfully mined at 11:25am AEST on Sunday 8 December, marking the 8th hard fork of the Ethereum network. As a non-contentious hard fork, all Ethereum clients agreed to and have implemented the software upgrade without major disruption to the network.
Istanbul includes six Ethereum Improvement Proposals (EIPs), specific code changes to the Ethereum protocol, including EIPs 152, 1108, 1344, 1844, 2028 and 2200.
However, like all good upgrades in the blockchain ecosystem, Istanbul has not been without controversy. Some in the community have criticised Istanbul as potentially introducing functionality or issues which will be incompatible with important aspects of Ethereum 2.0. Others have highlighted that Istanbul is likely to make a number of existing smart contracts break. Speaking on this, a developer for Parity (an Ethereum client used by around 23% of the network) Wei Tang commented that:
[Istanbul] will break at least a few deployed contracts... For software engineering, if you’re developing something that many people depends on, then backward compatibility is one of the top priorities for making any design decisions.
Istanbul represents another iteration of Ethereum 1.x, and brings the network one step closer to Ethereum 2.0, the planned major transition from a proof-of-work protocol to a proof-of-stake (PoS) protocol. Ethereum 2.0 is still a while off however, with Ethereum roadmap still providing that:
Ethereum 2.0 (Serenity) won't be fully rolled out for another 2-3 years with Phase 0 and Phase 1 due within 1-2 and Phase 2 due sometime in 2022. Ethereum 2.0 is being deployed as a separate blockchain so it does not supersede ETH 1.0 which means the chain needs to be sustainable for another 5-10 years.
This latest hard fork follows the successful implementation of the St. Petersburg and Constantinople hard forks in February. Further information about Ethereum 1.x, including the roadmap and details of team behind its development and upgrades can be found here.